In a recent article on the upcoming D&D Essentials line, Mike Mearls notes that a new rules update that will be released with the rules compendium will give Wizards miss effects with their encounter powers. The example that they used was that Burning Hands will now do half damage on a miss (and this seems to be whether or not you're playing the original class or the Essentials version of a Wizard). Personally, I'm really hoping that this change will affect not just Wizards, but all controllers (Druids, Invokers, Psions, and Seekers, as well).
As was brought up in the blog Square Fireballs, this would make for a perfect "controller feature" to unify all of the controller classes, much like all leaders get a minor action 2/enc heal, all defenders mark, and all strikers get bonus damage. Thus far, controllers have fulfilled their role almost solely through their powers. Technically they'd still be doing that with this feature, with the major difference being that their encounter powers simply work fundamentally differently from the encounter powers of other roles. The precedent of powers working differently has already been set with the Psionic classes that use power points (Psion, Ardent, and Battlemind).
Ideally, the miss effects would embody more than just half damage - after all, controllers are typically more about status effects. Half damage would be the easiest blanket errata to implement, but miss effects could also be implement without re-writing every single encounter power. Perhaps effects could be ranked, such that a power that dazes on a hit might slow on a miss. The penalties of debuffs could be halved on a miss. For effects that don't have an obvious "weaker version," a -2 attack penalty could be inflicted (fluff-wise, the enemy was able to shake off the effect but the effort distracted and/or drained them enough to compromise their offense). Or perhaps missed powers with effects could still inflict the original effects, but would instead deal no damage.
Overall though, even just half damage would be pretty nifty, as a controller would be making a positive contribution every time it used an encounter power, guaranteed. Given that controllers tend to have a lot of AoE's, multi-target attacks, and/or "splash damage" attacks, even missing the majority of targets would result in decent total damage spread out over multiple creatures. Plus their ability to destroy minions would be unparalleled, such that a Monk with Five Storms or a Swordmage with Sword Burst could no longer become just as effective a minion sweeper as a controller.
The only concern would be that this type of feature might place controller classes slightly above the power curve, relative to the other roles. Or perhaps I've just gotten used to the balance of power as it currently stands. I still hear plenty of complaints about controllers, even if I personally find them perfectly competitive and sometimes brutally effective.